The present invention describes an improved process for the extraction of an important biochemical, carnosic acid. The present invention more particularly describes an improved process for the extraction of carnosic acid from rosemary leaves a method of stabilizing the acid from decomposition and a method of preparing the acid in high concentration. Carnosic acid is characterized in its antioxidative function and is the most active ingredient in the prevention of the oxidation of fatty acids. The biochemical was found by Linde in 1962 to exist in slavia officinalis and by Wenkert in 1965 to exist in rosmarinus offinalis. Later the carnosic acid was found to exist also in other plants of the same family like s. scanariesis, s. sclarea and s. triloban. Carnosic acid is phenolic diterpene (C20H28O4) identified by Brieskorn and Domling in 1964 to be very potent antioxidant. Its antibiotic action against stephilococus and dental caries was also reported.
Numerous methods for extracting carnosic acid are described in U.S. Pat. No. 5,256,700 whose contents are incorporated by their mention. Further processes are found in the following U.S. Pat. No. 2,124,706; 4,012,531; 4,363,823; and 4,450,047.
It is the objective of the present invention to provide a novel process to extract carnosic acid from rosemary leaves. It is also the objective of the invention to provide a novel process to extract carnosic acid from rosemary leaves which stabilizes the carnosic acid from decomposition. A further objective of the present invention is to provide a novel process which affords very high concentrations of carnosic acid.
In accordance with the present invention there is provided a novel process to extract carnosic acid from rosemary leaves comprising treating the rosemary leaves with an aqueous solution of a lower alkyl alcohol in the presence of a water soluble acid and further optionally purifying the carnosic acid via extraction
The lower all alcohols found suitable for the present invention are chosen from the group consisting of methanol, ethanol, propanol, butanol, pentanol, and mixtures of these with ethanol preferred.
The lower alkyl alcohols are present in the extracting media in a concentration of 40% to 70% alcohol, preferably 55% to 65% alcohol, and most preferably 60% alcohol. The extraction using aqueous lower alkyl alcohols may be effected in one or more steps.
The water soluble acids found suitable for the present invention are selected from the group consisting of phosphoric acid and ascorbic acid, hydrochloric acid, acetic acid, citric acid and mixtures of these with phosphoric acid preferred. Said acids are present in a concentration of 0.1% to 30%, preferably 0.1 to 2%. The carnosic acid is removed from the aqueous alcoholic solutions by treating with vegetable oil, where almost any sort of vegetable alone or in combination with another vegetable oil can be used.
The carnosic acid dissolved in the vegetable oil may be further concentrated by extraction using a buffer of disodiumtetraborate at a pH range of 7.5 to 9.5, prefersbly 8.5 to 9.5 to afford carnosic acid in concentration of as high as 80% to 90%.
Examples 1,2,6 to 8 show the process of extracting with alkyl alcohol and the good yield obtained. Examples 3 to 5 are comparative Examples showing the lower yield obtained using other organic solvents.
Example 9 together with Table 1 shows the effect of the acid on the stability of the carnosic acid and the advantages of ascorbic acid and phosphoric acid, especially phosphoric acid.
Example 10 shows how the concentrations of carnosic acid may be increased through successive extraction in the presence of a buffer of disodiumtetraborate.
The present invention specifically describes the selective extraction of carnosic acid directly from the plant using an acidic polar solution containing water, lower alkyl alcohol and acid. The use of this particular extraction solution is very beneficial with regard to the following results: a) High yield of camosic acid in the concentrate. b) Extraction of the carnosic acid is very selective. Very few other chemicals such as pro-oxidants from the plant are extracted. c) Further oxidation of the carnosic acid to carnosol or in the extraction process is prevented. In addition the carnosic acid is stable for a period of more than 24 hours in this solution d) The high distribution coefficient of the extracting solution results is effective extraction process of carnosic acid. Following the extraction the carnosic acid moves to the apolar phase as a result of the change in the distribution coefficient of the solution as the alcohol is evaporated. Control of the alcohol concentration in the solution enables the undesirable fractions that will move to the polar phase. As an apolar phase one can use a non carnosic acid. Alternatively the polar phase can be some volatile solvent thus enabling the crystallization of the carnosic acid.
While the invention will now be described in connection with preferred embodiments in the following examples, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents, as may be included within the scope of the preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are way of example and for purposes of illustrative discussion of preferred what is believed to be the most useful and readily understood description of procedures, as well as of the principles and conceptual aspects of the invention.